Electrical discharge device of the magnetron type



P. L. SPENCER 2,478,644

-3 Shqets-Sheet l ELECTRICAL DISCHARGE DEVICE OF THE MAGNETRON TYPE l {,1 wmmumumfii :7

Aug. 9, 1949.

Filed Oct. 25, 1943 P. L. SPENCER Aug. 9, 1949.

. ELEQTMQAL DISCHARGE DEVICE OF THE MAGNETRON TYPE Filed Oct. 23, 19439 3 Sheets-Sheet 2 MIME/V7015 fz'lfav L. 5Pf/VCL'K, fly U P. L. SPENCER Aug. 9, 1949.

'EL'EC'YI'IRJQIUCAL DISCHARGE DEVICE OF THE MAGNETRON TYPE Filed Oct. 25, 194:5

I 3 Sheets-Shec 3 a W 0 C %T TN M .fl 9w #5 ML w 3 n V1 2 5 Q 7 k R mm Patented Aug. 9, 1949 -MAGNETRON BE.

v Percy hrSpencer WeSt Newton, Mass, a'ssignor .to Ra'yLtheonManfifacturingICornpaiiy, Newton, "'Ma ss., a corporation of'Delaware 1 mp licationsoetotenea, 1943,.Serial No. 561,450

plurality of oscillating ;circ.uits, all: of hichare intended to :oscillate. at the; same ireduency vand thus to contribute :to: the effective output of -.the magnetron. Z-Heretofore difficultiesihave been on,- counto-red inconstructing each of the :ioscillatin cix cuitsl to have-exactly the same natural -fre-' eency and'lp ovid nszasufficiently closeardou ing.

between ;a 1l.;of these circuits ,-;so that small differences in, the constants: of the circuits would be overoomezand allofthecirouits oscillate at the :same output frequency sWith maximum effectiveness. fIn suchmagnetrons-also aitendenoy has;existed for the -,device to oscillate various spurious mo,des;i n:additionto the principal mode which determines ;the desired 1outpnt frequency.

A-n object of :this -;inventi-on 1118, ;to. devise ;a magnetron; of the foregoing: type: in whichutlle probability ofv exactwequivalence gin 'thenna-tural freq ency (of geachmf thewpossibleioscillating cir cuits thereiniisygreatlylincreased. 1

gAn-othen obj ect is to. devise ianitarrangement :in which all 10f the: oscillating!,cirouits: are closely coupled rthrough the; shortest possible; path.

Another object iis zsto devise :su'ch eanrarrangee went in whichgthe possibility ioi "Ttheil device to oscillate Y lII..-l11'ldeSl1LQdSpuri011S modes reduced substantially .to :1 azminimum.

MA :furtherroloj ect .is :to .devisezanxarrangement inivvhich; athe mouplingtetween the oscillating portion: of;the device :and the ;output .is substantially; increased.

A stilllfurther object is Ito deviseanearrangee mentgwherebyvafl of the possible ioscill'aiting; circuitsmay be tuned .in a;simple and rdirectananner. r

The foregoing andwother' objects ofthisinvention vvill be' best understood f-rom-- the following description of exemplifications there-of; reference being-had to the accompanyingflrawings;wheret Fig. 2' is a transverse crosseseojtion taken along -=Eig. 3- is .a perspective view of the tw'o halves ofzthelanodestructureseparated from; each other,

the upper halfipartly broken away;

' ilig. Azis -,a. '.long.i-tudinalcross-section of ian other embodiment of my. invention and 1 Fig. 5 is- -a 'perspective view 10f: the; :lowen LSACIaiinSA (c1. 215;4'0)

of the magnet structure of .the arrangement shown in Fig.4.

The magnetron comprisesian anode illustrated in Eigsjl; P2 arldi'S. structure consistingof two halves I and l, each oonstructed of a-; sLiita5le highly-conducting material, such as copper and \in ringliorm' aiqha l h zaee h l h it ei e ji with a, central openin esia assemb ed; together forniragcentral oreA extendm n thesamdestructurehhddonning egc'haniberlwith- 1 inwhich aoathode 5 pr ably o f the indirectlyheated thermionic typeg s ppoitedlL .Eaclia d ;formed with an: outerfubstandmg in zfi ee s .s V l cavity section] in thelo ver (anode half "2'. inneniaeesof the upstanding fingersfl constitute anode ;p0r-.t io ns adapted to {receive ie'lect'rohs emitteddrom the cathode -5. i Thelupp'erano'de halfglx' fingers :9 z roiect ne i m r, e l me-si :b -J cavity-isectionfl; Iheifingers fl and; '9 sr erc usi y 1 The spaced amund their; respective openings edges :of the sections 6 are adapted to he brought into contact with each other. in slih ethat I each of ,the fingers f9ois Sl 8CE db ringsz lllweachmrovided.vvith anendLcapillJ lines in-Eig. 3 ;*When the two-lanode-hal ves 2 areassembledin thjs -vvay thelan .de tur zisyhermeticall 'y oinedalong the ot ed esiof in rni kr blibv s l sozassto fonrnagnitary; anode assembly. In order-to complete ,the tube assembly; lthe anode istructure; .is provided with impa r I end The. ringsw'iill and caps I 1-, I are likewise; adaptedtolbe hermetically sealed in iplaca preferablir, by silver soldering The-cathode "5 =islpr0videdlw1thf Ofg ,ileads $1.122 :and 4 3 .rCQEQBQtQd' to t .the' 1 ite" en'dsa-of an=:inter rialcheater 5a. ,Qne of "t leads;iomeXamp-le v likewise adapted .,t be I electrically con-neetedto the-.-outer .cond 1id g I1 and proper voltages are applied thereto, oscillations are generated within the anode structure.

It will be noted that when the upper and loweranode halves I and 2 are joined together, they form an annular chamber I8 through which the oscillations generated are readily propagated, and which in effect constitutes an annular cavity resonator. The oscillatory energy which is propagated through the annular chamber I8 may be led 01f to a suitable utilization device by means of a coupling loop I9 which extends into the annular chamber I8. and couples to the magnetic component of the oscillatory fields set up Within said annular chamber. One end of the coupling loop I9 is connected to the inner end of a conducting pipe 20 hermetically sealed through an opening ZI in the side of the anode structure. The other end of the coupling loop I9 is connected to a conductor 22 which passes through the pipe 2|] and emerges therefrom through a glass seal 23 carried at the outer end of said pipe. The conductor 22 together with an external pipe, not shown, which may be connected electrically to the pipe 20, form a concentric transmission line through which the oscillations may be conducted to any suitable load device.

When the tube described above is in its oscillating condition, the fingers 8 and 9 are of opposite phase so that oscillating currents tend to 'fiow between alternating fingers 8 and 9. It will be noted that a conducting circuit extends between each finger 8 and its adjacent finger 9, and that this circuit in each case extends in a circular path through the wall of the annular chamber I8. Such a circular path contains a definite amount of inductance. Likewise a capacity exists between the adjacent fingers 8 and 9. Thus each of the above circuits constitutes tuned oscillatory circuits whose natural frequency is determined by the inductance and capacity thereof. As already indicated, the fingers 8 and 9 are of opposite voltage phase so that when a finger 8 is positive, the adjacent finger 9 is negative, and on the next half cycle the voltage conditions are reversed. Therefore oscillatory currents will flow between the fingers 8 and 9 through the walls' of the annular chamber I8 in a direction to create an annular magnetic field in said annular chamber. All of said currents are in phase with each other, and thus all of said magnetic fields are likewise in phase, producing a strong resultant annular magnetic field. This resultant annular magnetic field couples all of the oscillating circuits, and thus tends to make the inductance of all of said oscillating circuits equal. It is comparatively simple to construct the arrangement so that the capacity between each pair of anode fingers is likewise equal. Therefore, in the above arrangement, the device, due to its structure, tends to make the natural frequency of each of the oscillating circuits exactly equal. In addition, the magnetic field closely couples all of the oscillating circuits by the shortest possible path, producing a very close coupling which forces all of said oscillating circuits to oscillate exactly at the same frequency, even though slight difierences in the natural frequencies of said circuits might otherwise tend to exist.

As pointed out in'my copending application, Serial No. 421,145, filed December 1, 1941, and now U. S. Patent No. 2,417,789, granted March 18, 1947, tendencies have existed for magnetrons of the multiple anode type to oscillate in various spurious modes, which tendency can be substantially eliminated by directly interconnecting alternate anode electron-receiving sections by a low impedance connector, which arrangement is known as strapping. It will be seen that the fiat end wall of anode half I directly electrically ties together the anode fingers 9, while the fiat end wall of the anode half 2 directly electrically ties' together the anode fingers 8. It will fur-- ther be noted that these fiat anode end walls: constitute connectors of very low impedance. In;

this way the structure accomplishes a strapping action in a very effective manner.

The coupling loop I9 is directly coupled with the annular oscillatory magnetic field in the annular chamber I8. In this way the energy of each. of the oscillating circuits is fed in the most direct; path possible into said coupling loop, which thereupon feeds this energy through the conductor 22 as a part of aconcentric transmission line to a suitable load device.

Instead of the arrangement as shown in Figs. 1 and 2, my invention lends itself to the construction of a very compact type of device, as is illustrated in Figs. 4 and 5. In these figures, the same reference numerals which are used in Figs. 1, 2 and 3 are applied where the elements are substantially identical. In Figs. 4 and 5 the central bore 4 of the anode structure is closed directly by the pole pieces of a magnet structure 24. This magnet structure is preferably made of a material of high magnetic retentivity formed as a permanent magnet. The magnet structure may likewise be formed of an upper half 25 and a lower half 28. The upper half 25 is provided with a pole piece 21 fitting into and hermetically soldered in a corresponding recess in the top of the upper anode half I. The lower magnet half 25 is likewise provided with a pole piece 28 fitting into and hermetically soldered in a corresponding recess in the bottom of the lower anode half 2. Each of the magnet halves 25 and 26 is formed with an upstanding rim portion 29, the edges of which are adapted to be brought into contact with each other when the magnet poles 21 and 28 are soldered in place on the anode structure. In order to assist in holding the two magnet halves 25 and 26 together, each magnet half may be provided with a series of bolt-holes 30, as shown for example in Fig. 5, through which suitable bolts 38a, may extend and firmly clamp the magnet structure in place on the anode structure. The arrangement, as shown in Figs. 4 and 5, lends itself to the utilization of a novel cathode construction, as described and claimed; in the copending application of William C. Brown, Serial No. 503,622, filed September 24,. 1943, now Patent Number 2,416,899. The oath-- ode proper comprises a tubular conducting sleeve 3I coated with the usual electron-emitting oxides.

Within the sleeve 3I is supported a suitable filamentary heater 32, one end of which is electrically connected to the top closed end of the sleeve 3|. The sleeve 3I is formed with a lower reduced tubular end 33 which passes through an opening 34 formed in the pole piece 28. The low-er end of the reduced tubularsection 33 fits into a recess in the upper end of a conducting rod 35 provided with a bore 36 leading to the interior of the hollow cathode structure. The bore 36 is provided with a side opening 31 through which an insulated wire 38 connected to the lower end of the heater 32 projects. The conductors 35 and 38 thus form the lead-in connections for supalso for supplying a biasing vpotential to, the

atifedi 'rfie conadctcr roa 35% ri'glulys m toramendcupssi ,ofi?cofldllctive*mateflaPbWsult able means; such "asan eyelet ailai" The conduittor .38fpassesithroughfan eyelet ma e-d m se The cup 39 1s insulated fromthe'lower magnethalf-l Gb'y means-t of a glass tube 42 which has one end hermetically sealed to theiuppe'r endorthe c'ufiss Tiie opposite en'd'of theglass tube 42- is' similarly sealedito a tubular metal shell 43? The"-upper-end of said metal shell is"inserte f'into "an-*'enlarged cad -of the opening '8 "the -lowermagnet hermeticallyjoinedtherewith as; by br lower. magnet ihalff'l!6 togather with 'thecatliode 1,-

of "the' capacity or inductance values ofsaid n nularlchamber l8rwill produce a corresponding change "inth"e' natural ffequency of the oscillating system, andwthus produce.,a -tuning of the entire device. While variations in"these impedance constants of the arrmilarrchamberislaimay 6, tniisenanse tiie nataral annularwhamb'ers and' th us ach thlez o'soil-=1 latflfg circuits thereifi nd to oscillatei I It will be noted that the uppen-and lower: mag" net-halves 25 and 26' are formedti with suitablee o enings is and 5fitnrough wliichi thei ipesi200 and projc mme": nderstood' that thisfin vefition is notfl ite to the' particular details? as 'described 'above as-maiiyequivalents wllbfsu gest themselves to th'o'se skill'd finithearti ltfis'c accordingly desired thatetheappended clainis be iven a brba'd f "te'rpretatioricommensuratee with the 'scop'e of l'l'i invention within the artii- What isclaimed ise Y lf-An electroh discharge fojecting alternat'ely from upper and alves' -ofsai body andadyingin: -the sur I:

' atpair of ririgs'sextehdingi? 'saidabodyt cap mentbers closing' the ou er ends ofsari rings'g and a pair of ca'thode l'eads 'electrically: connectd to sai'd-i be carried out in any suitablexmanneraksuchi as;--

those which have vbeendeveloped-um connection with the tuning'of "cavityresonators 'a preferred arrangement for accomplishing such tuningriis'; also illustrated-in- Fig. 4.'-.=1 Eorrath'is puiipo'sei a coupling loop 44 similar to 2th upling' oopdl 9 is inserted: into-the-annulan' hamber I end of the: coupling. loop 44 istconnecte inner end-of a hollowlpipe45zhermlticall through an 'openingcin the side wall. of the anode structure.'-* The other end. of thelz'couplingsloop 44 is connectedetoaa conductortflirwhich extends through a glass seal 4T'car'ried'at the outer end of the p'ipe 45. Surround-ing -the conduct-ch46? particularly as-- it-- emerge's'ssfroin -fthe glass 'se'al 41;" is a hollow"tubular condiicting membenflfl which may be screw-threaded onto a portion of the pipe 45 and thus supported in place substantially concentric with the conductor 46. The outer end of the tubular member 48 may be closed by an end plug 49 which may serve as a centering and supporting member for the outer end of the conductor 46. The hollow member 48 together with the conductor 46 may be caused to function as a tuning chamber by providing a tuning plu 50 filling the space between the conductor 46 and the hollow member 48, and being adjustable along said hollow member 48. This adjustment may be provided by means of a set screw 5! received into one side of the plug 50 and projecting through a slot 52 in the side of the hollow member 48. The plug 50 may be adjusted along the hollow member 48 to impart to said member the proper characteristics, and may then be secured in place by tightening the set screw 5!. By proper dimensioning of the hollow member 48, the hollow chamber formed therein, as defined by the position of the plug 50, may be caused to reflect either inductance or capacity into the tubular chamber l8, and

through said? ringssaid cathode: 'leads- -lyingiin=i planes 1 intermediate; said anode'i structure and i said::caps:: ia 7 V 2;i-:An :;electrom discharge-idevice comprising teacathode ariri anod'eestructuret SDHkCBd/I' from: and concentrically disposed about same-cathode;-'2-said:: anode :structure including i-zan annular 'cavity resonator-chairing'rawcentralopening definedb y-r a-s pluralitycrof overlappi'ng electron-receiving" anode :portidn's :proj'ecting :alt'e'rnately irom up peir'ssand-lai lowerf halves s-of s"=sa-idi ca'vity resonator and lying in the surfac 01 acylinderz a pair of ringsrsextending fr'om opposite sides: of 'said cavityc resonator; zcap members closing the cuter endsfOfis-"saicl ringsa pair 'of cath'ode" eads' ele trically: connected to said cathod fand: 'ext'en saidscathode leads lyingdn plan'e's intermediate= saidiianodei=structure and *said "caps arid meanss extendingsiinto 'saidcavity resonator;- for" cabl ings-zelectricali'oscillations generated thereiri out c nsaididevice.

3'3 An a-e1ectron discharge;device eoniprlsing2- a cathode; an anode structure spaced from and concentrically disposed about said cathode; said anode structure including an annular cavity resonator having a central opening defined by a plurality of overlapping electron-receiving anode portions projecting alternately from upper and lower halves of said cavity resonator and lying in the surface of a cylinder; a pair of rings 0 extending from opposite sides of said cavity resonator; cap members closing the outer ends of said rings; means, extending into said cavity resonator, for leading electrical oscillations generated therein out of said device; and means,

55 carried by said cavity resonator and also extending therein, for varying the reactive impedance constants thereof to tune said device to a predetermined frequency of oscillation.

4. An electron discharge devicecomprising: a cathode; an anode structure spaced from and concentrically disposed about said cathode; said anode structure including an annular cavity resonator'having a central opening defined by a plurality of overlapping electron-receiving anode portions projecting alternately from uptrequency at whicli saideper and lower halves of said cavity resonator;

and lying in the surface of a pair of rings extending from opposite sides of said cavity resonator; cap members closing the outer ends of said rings; a cylinder; 2. second cavity resonator carried by and coupled to said first-named cavity resonator; and means, slidably mounted within said second cavity resonator, for altering the reactive impedance constants thereof, and thereby tuning said deviceto a predetermined frequency of oscillation.

5. An electron-discharge device comprising: a cathode; an anode spaced from said cathode and incorporating a cavity resonator; and a pair of opposed magnetic members disposed, respectively, on opposite sides of said anode to establish a magnetic field theret-hrough in a direction transverse to the discharge path between said cathode and said anode; each of said magnetic members being of E-shaped cross-section and including a central leg constituting a pole piece of one polarity, and a pair of outer legs of opposite polarity in contact with the outer legs of the other of said magnetic members to complete the path of saidmagnetic field.

6. An electron-discharge device comprising: a cathode; and an anode structure spaced from said. cathode; said anode structure includin a base portion having an annular recess therein, an upstanding lip extending from one side of said recess, and a plurality of electron-receiving anode portions projecting from the other side of said recess; a ring extending from the side of said base portion opposite said lip and anode portions; a cap member closing the outer end of said ring; and-a cathode lead electrically connected to said cathode and extending. ex-. teriorly of said device through said ringysaid cathode lead lying in a plane intermediate said anode structure and said cap.

7. An electron-discharge device comprising: a cathode; and an anode structure spaced from said cathode; said anode structure including a pair of base portions each of which has an annular recess therein, an upstanding lip extending from one side of each of said recesses, and a plurality of electron-receivin anode portions projecting from the other side of each of said recesses; adjacent electron-receiving anode por-.

tions overlapping each other and lying in the surface of a cylinder; a rin extending from the side oteacli of said base portions opposite said lipganode portions; anda cap member closing the outer end of each of saidvrings; and a pair of cathode leads electrically. connected to said cathode and extending exteriorly of said device through/said rings; said cathode leads lying in planes intermediate said anode structure and said caps. a

8. An electron-dischargedevice comprising: a cathode; an anode structure spaced from said cathode; :said anode structure'including a pair of base portions each of which has an annular recess therein, an upstanding lip extending from one side of each of said recesses, and a plurality of electron-receiving anode portions projecting from the other side of each of said recesses; adjacent electron-receiving anode portions overlapping each other and lying in the surface of a cylinder; said base portions, together with said lips and said electron-receiving anode portions, defining a cavity resonator; a

pair of rings extending from opposite sides of said cavity resonator; cap members closing the outer ends of said rings; a pair of cathode leads electrically connected to said cathode and extending exteriorly of said device through said rings; said cathode leads lying in planes intermediate said anode structure and said cap and means coupled with said'cavity resonator for leading oscillations generated therein out of said device.

PERCY L. SPENCER.

REFERENCES CITED The following references are of record in the file of this patent:.

UNITED STATES PATENTS Number Name Date 2,115,521 Fritz et a1; Apr. 26, 1938 2,144,222 Hollmann Jan. 17, 1939 2,209,923 Kilgore July 30, 1940 2,295,396 George Sept. 8, 1942 2,409,222 Morton Oct. 15, 1946 2,411,151 Fisk Nov. 19, 1946 2,424,886 Hansell July 29, 1947 FOREIGN PATENTS Number Country Date 215,600 7 Switzerland Oct. 16, 1941 215,602 Switzerland Oct. 1, 1941 Certificate of Correction Patent No. 2,478,644 August 9, 1949 PERCY L. SPENCER It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: 1

Column 7 line 2, after a and before pair insert cylinder; 0; line 5, strike out the words and semicolon a cylinder; column 8, line 2, for anode portions; and a read and anode portions; a; line 28, for cap read caps;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 10th day of January, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

